JP2014509786A - Calibration of device performance in integrated circuits. - Google Patents

Abstract

  A multi-finger device (105) for implementation in an integrated circuit is first deactivated at the same time as the first finger is active, with the first finger configured to remain active. A second finger of the multi-finger device (105) is selectively activated in response to determining that the degradation measurements for the second finger and the multi-finger device (105) satisfy a degradation threshold And a finger activation circuit (125) configured to:

Description

One or more embodiments disclosed herein relate to an integrated circuit (IC). More particularly, one or more embodiments relate to the calibration performance of devices that include multi-finger in an IC.

Background Designing reliable circuits is very complex, especially in aggressively reduced complementary metal oxide semiconductor (CMOS) technology. For example, modern IC manufacturing processes capable of manufacturing small devices increase the possibility of interface traps in P-type metal oxide semiconductor (CMOS) devices during long-term negative bias stress. An interface trap is generated when a negative voltage is applied to the gate of a PMOS device for an extended period of time. The interface trap is placed near the Si oxide / Si crystal lattice boundary where holes or positive charges remain, thereby causing a threshold voltage shift of the PMOS device. Hole trapping generates a fixed charge along with the interface state. Both are positive charges, resulting in a negative shift in threshold voltage. This phenomenon is called PMOS negative bias temperature instability (NBTI). NBTI has more impact on PMOS devices than N-type metal oxide semiconductor (NMOS) devices. However, a phenomenon called positive BTI (PBTI) affects NMOS devices.

  In light of the trend toward reduced device size and voltage margin in modern IC designs, phenomena like BTI for NBTI and / or PBTI can be an important factor limiting the lifetime of CMOS devices. Other phenomena such as hot-carrier injection (HCI) can combine with BIT to greatly reduce the lifetime of CMOS devices. Because of the phenomena shown, circuit designers must overdesign the device to compensate for degradation that occurs over the lifetime of the device. A circuit designer, for example, creates a device in an IC that has operating characteristics that are different or better than those required by the circuit specifications.

  When a device is over-designed, the device operating characteristics, such as power usage, area usage, performance, etc., can vary significantly from the established target characteristics of the device as specified in the circuit specifications. As a result, if not unsuitable, the device is less than optimized for the intended purpose of the device, and over-design, especially when applied across many devices in modern ICs, Costs for design can also be added.

Summary One or more embodiments disclosed herein relate to integrated circuits (ICs), and more particularly to calibrating the performance of devices that include multiple fingers within an IC.

  An embodiment of a multi-finger device for implementation in an integrated circuit is first deactivated at the same time the first finger is configured to remain active, and the first finger configured to remain active A finger configured to selectively activate the second finger of the multi-finger device in response to determining that the degradation measurement for the second finger and the multi-finger device satisfies a degradation threshold. And an activation circuit.

  In some embodiments, the multi-finger device further comprises a switch coupled to the second finger, wherein the switch converts the second finger gate to a data signal that is also coupled to the first finger gate. Selectively combine.

  In some embodiments, the finger activation circuit includes a control circuit configured to provide a control signal to the switch in response to detecting the degradation threshold.

  In some embodiments, the finger activation circuit further comprises a monitor circuit configured to detect a degradation threshold by determining an amount of time that the first finger of the multi-finger device is active. Including.

  In some embodiments, the monitor circuit compares a count of the number of clock cycles in which the first finger of the multi-finger device is active to a degradation threshold and is responsive to the count being greater than or equal to the degradation threshold. And configured to instruct the control circuit to activate the second finger.

  In some embodiments, the finger activation circuit detects a degradation threshold by measuring an operational parameter of the multi-finger device in the field, compares the operational parameter to the degradation threshold, and the operational parameter is A monitor circuit configured to instruct the control circuit to activate the second finger in response to determining that the degradation threshold is met.

  In some embodiments, the operating parameter is the threshold voltage of the multi-finger device, and the degradation threshold defines a threshold voltage level that is greater than a threshold voltage reference level.

  In some embodiments, the operating parameter is the drain saturation current of the multi-finger device and the degradation threshold defines a level of drain saturation current that is less than the reference level of drain saturation current.

  In some embodiments, the gate of the second finger is coupled to the power supply potential of the integrated circuit when not active.

  A method of calibrating the performance of a multi-finger device in an IC includes determining a degradation measurement for the multi-finger device in the IC and comparing the degradation measurement with a degradation threshold. In response to determining that the degradation measurement meets the degradation threshold, the fingers of the multi-finger device may be activated.

  In some embodiments, the method includes selecting a degradation measurement to include an amount of time that the multi-finger device is active, and selecting a degradation threshold to be a predetermined amount of time. Further included.

  In some embodiments, the method further includes determining an amount of time that the multi-finger device is active according to the number of clock cycles counted in a counter implemented in the integrated circuit. The number of clock cycles is compared to a clock cycle number threshold that represents a predetermined amount of time for the degradation threshold.

  In some embodiments, the method includes selecting a degradation measurement to include a multi-finger device threshold voltage, and a multi-finger device threshold voltage greater than a reference level of the threshold voltage. Selecting a degradation measurement to be a level.

  In some embodiments, the method includes selecting a degradation measurement to include a drain saturation current of the multi-finger device and a level of the drain saturation current of the multi-finger device that is less than a reference level of the drain saturation current. Selecting a degradation measurement to include.

  In some embodiments, the multi-finger device comprises a primary finger that is active prior to activation of any additional fingers of the multi-finger device.

  In some embodiments, activating the fingers of the multi-finger device further comprises activating a plurality of fingers of the multi-finger device.

  An embodiment of a system configured for implementation in an integrated circuit is such that a first finger configured to remain active and deactivated at the same time as the first finger is active. A multi-finger device including a second finger initially configured and a switch coupled to the gate of the second finger. The switch activates the second finger by coupling the gate of the second finger to a signal that is also coupled to the gate of the first finger, and decouples the second finger gate from the signal. Configured to deactivate two fingers. The system further comprises a finger activation circuit configured to instruct the switch to activate the second finger in response to detecting a minimum amount of degradation in the device.

  In some embodiments, the switch may couple the gate of the second finger to the power supply voltage of the integrated circuit when not active.

  In some embodiments, the finger activation circuit comprises a control circuit coupled to the switch. The control circuit is configured to provide a control signal to the switch. The finger activation circuit further comprises a monitor circuit configured to detect a minimum degradation in the device and provide a signal to the control circuit in response thereto.

  Other embodiments may include multi-finger devices configured for implementation within an integrated circuit. The multi-finger device may comprise a first finger configured to remain active and a second finger that is initially deactivated at the same time that the first finger is active. The second finger may be configured to activate during operation of the integrated circuit.

  In some embodiments, the multi-finger device is configured to selectively activate a second finger of the multi-finger device in response to detecting minimal degradation in the multi-finger device. The circuit further includes a circuit. The second finger is initially deactivated and activated in response to detecting minimal degradation of the multi-finger device.

  In some embodiments, the multi-finger device further comprises a switch coupled to the second finger, wherein the switch causes the gate of the second finger to be a data signal that is also coupled to the gate of the first finger. Selectively combine.

  In some embodiments, the finger activation circuit may further include a control circuit configured to provide a control signal to the switch in response to detecting a minimum degradation.

  In some embodiments, the finger activation circuit may further include a monitor circuit configured to detect minimal degradation by determining an amount of time that the first finger of the multi-finger device is active. .

  In some embodiments, the monitor circuit compares a count of the number of clock cycles in which the first finger of the multi-finger device is active to a degradation threshold, and the count is greater than or equal to the degradation threshold. In response, it may be configured to instruct the control circuit to activate the second finger.

  In some embodiments, the finger activation circuit detects the minimum degradation by measuring the operational parameter of the multi-finger device in the field, compares the operational parameter to the degradation threshold, and the operational parameter is degraded. A monitor circuit configured to instruct the control circuit to activate the second finger in response to meeting the threshold may further be included.

  In some embodiments, the operating parameter may be a multi-finger device threshold voltage, and the degradation threshold defines a threshold level that is greater than a reference level of the threshold voltage.

  In some embodiments, the operating parameter may be the drain saturation current of the multi-finger device and the degradation threshold defines a level of drain saturation current that is lower than a reference level of drain saturation current.

  In some embodiments, the gate of the second finger can be coupled to the power supply potential of the integrated circuit when not active.

1 is a first block diagram illustrating a system for calibrating a multi-finger device according to an embodiment disclosed herein. FIG. FIG. 2 is a second block diagram illustrating the system of FIG. 1 according to another embodiment disclosed herein. FIG. 3 is a third block diagram illustrating the system of FIG. 1 according to another embodiment disclosed herein. 6 is a first graph illustrating calibration of a multi-finger device according to another embodiment disclosed herein. 6 is a second graph illustrating calibration of a multi-finger device according to another embodiment disclosed herein. 6 is a first flowchart illustrating a method for collecting calibration data for a device in an IC according to another embodiment disclosed herein. 6 is a second flowchart illustrating a method for calibrating a multi-finger system according to another embodiment disclosed herein.

DETAILED DESCRIPTION OF THE DRAWINGS While the specification concludes with claims that define the features of one or more embodiments that are considered novel, the one or more embodiments may not be considered in view of the description in conjunction with the drawings. It is believed to be further understood. Depending on requirements, one or more detailed embodiments are disclosed herein. However, it should be understood that the one or more embodiments are merely exemplary. Accordingly, specific structural and functional details disclosed herein are not to be construed as limitations, but merely as a basis for the claims and in any suitable detail structure that is hypothetical. It should be understood as a representative basis for teaching one of ordinary skill in the art to variously employ one or more embodiments. Furthermore, the terms and phrases used herein are not intended to be limiting, but rather are intended to provide an understandable description of one or more embodiments disclosed herein. Is.

  One or more embodiments disclosed herein relate to integrated circuits (ICs), and more particularly to the calibration performance of devices that include multiple fingers within an IC. A multi-finger device can be controlled to selectively activate one or more of the device's fingers over time. Activation of fingers that have not been previously activated in a multi-finger device attenuates the effects of device degradation that occurs over time, eg, with the lifetime of the multi-finger device.

  For example, if the multi-finger device degrades by a first amount, one or more inactive fingers are activated, thereby restoring the multi-finger device to or near the operating state prior to degradation. Over time, as the multi-finger device continues to degrade, eg, by a second amount, one or more other inactive fingers may be activated. By activating additional fingers of the multi-finger device over time, the amount that multi-finger devices must be over-designed in the context of circuit design can be reduced. As a result, the device becomes more suitable for its intended function.

  One or more embodiments disclosed herein may be applied to one or more devices in an IC. For example, one or more embodiments of the circuit design may be selected as critical or essential to the function of the circuit design within the IC in which the device is to be implemented. For example, a very important device may be implemented in or as part of a current mode logic buffer. In any case, those devices that are recognized as critical or essential in circuit design can be calibrated to control device degradation over time.

  FIG. 1 is a first block diagram illustrating a system 100 for calibrating a multi-finger device according to embodiments disclosed within this specification. As shown, the system 100 may include a multi-finger device 105, a plurality of switches 110, 115, 120, and a finger activation circuit 125. In embodiments, the multi-finger device 105 can be a multi-finger transistor.

  Multi-finger device 105 is characterized by including a plurality of fingers. In general, the term “finger” refers to a number of gates or gate regions included in a particular metal oxide semiconductor field effect transistor (MOSFET). As shown, multi-finger device 105 includes a plurality of gate regions 140A-140D, a plurality of source regions 130A-130C, and a plurality of drain regions 135A-135B. For illustrative purposes, the surrounding well and substrate regions are not shown.

  Each of source regions 130A-130C may be coupled in parallel to a node of a circuit (not shown) shown as a source circuit node in FIG. Source regions 130A-130C may be coupled to a source circuit node via metal wiring that couples to one or more contacts (not shown) in each one of source regions 130A-130C. Similarly, drain regions 135A-135B are coupled in parallel to a node of a circuit shown as a drain circuit node. Drain regions 135A-135B may be coupled to the drain circuit node via metal interconnects that couple to one or more contacts (not shown) in each one of drain regions 135A-135B.

  For illustrative purposes, the multi-finger device 105 includes four fingers. The fingers of multi-finger device 105 are numbered consecutively 1-4 for reference. The finger 1 can include a gate region 140A, a source 130A, and a drain 135A. Finger 2 can include a gate 140B, a drain 135A, and a source 130B. The finger 3 can include a gate 140C, a source 130B, and a drain 135B. Finger 4 may include a gate 140D, a source 130B, and a drain 135C.

  Finger 1 is referred to as the primary finger because finger 1 remains coupled to the gate circuit node. In the example shown in FIG. 1, no switch is used to selectively couple the gate region 140A of finger 1 to the gate circuit node. However, it should be understood that the elimination of the switch is for illustrative purposes. In one embodiment, additional switches for selectively coupling gate region 140A to the gate circuit may be included as described for gate regions 140B-140D.

  Each of the fingers 2-4 is referred to as a secondary finger because each is initially deactivated while the finger 1 is initially active. Each of fingers 2-4 can be selectively activated through switches 110-120, respectively. Each of the switches 110-120 can be implemented as any of a variety of different switching circuits, ranging from a single transistor switch to a more complex switch that includes multiple elements and / or transistors.

  The finger activation circuit 125 can independently control the opening and closing of the switches 110-120 via the control signal 145, thereby activating or deactivating each of the fingers 2-4. Specific conditions for activating fingers 2-4 are described in more detail herein. Initially, multi-finger device 105 starts operation with each of switches 110-120 being open. Accordingly, finger 1 is active, while fingers 2-4 are deactivated. In this state, finger 1, eg, gate region 140A, is coupled to the gate circuit node, but gates 140B-140D are not coupled to the gate circuit node.

  In this specification, the same reference numerals are used to refer to terminals, signal lines, wirings, and their corresponding signals. In this regard, the terms “signal”, “wiring”, “connection”, “terminal”, and “pin” may sometimes be used interchangeably within this specification. Also, the terms “signal”, “wiring”, etc. may represent one or more signals, for example, carrying a single bit through a single wire, or carrying multiple parallel bits through multiple parallel wires. Should be understood. Further, each wire or signal may in some cases represent bi-directional communication between two or more elements connected by the signal or wire.

  Switches 110-120 are shown as being in an open state in which each of gate regions 140B-140D is not coupled to a gate circuit or ground. In one embodiment, when a finger is deactivated, the gate of that finger can be coupled to the IC supply voltage. In this example, multi-finger device 105 is an N-type metal oxide semiconductor (NMOS) device so that when the corresponding switch is open, the gate region of each inactive finger is at ground, eg, the lowest or lowest IC. Can be coupled to a low supply voltage. If the multi-finger device 105 is shown as a P-type metal oxide semiconductor (PMOS) device, the gate region of each inactive finger is coupled to the high supply voltage of the IC when the corresponding switch is open. It should be understood.

  Over time, as multi-finger device 105 suffers from degradation, one or more or all fingers 2-4 may be activated. In response to determining that a sufficient amount of degradation has occurred in multi-finger device 105, finger activation circuit 125 may activate one or more or all multi-finger devices 105. For example, initially, at time T1, only finger 1 is active and gate region 140 is coupled to the gate circuit node. No deterioration has occurred at the start of the operation of the IC and device 105, for example, at time T1.

  At time T2, the finger activation circuit 125 may determine whether the multi-finger device 105 is degraded, for example, a first minimum amount of degradation. In response to determining that multi-finger device 105 has a first minimum amount of degradation, finger activation circuit 125 directs switch 110 to close through control signal 145. When switch 110 is closed at time T2, gate region 140B is coupled to the gate circuit node and finger 2 is activated. It should also be understood that at time T2, switch 110 disconnects gate region 140B from ground. By activating both fingers 1, 2, the first minimum amount of degradation of multi-finger device 105 can be overcome. For example, the degradation index of the multi-finger device 105, eg, any index used to determine degradation measurements, is at or near the reference level for that index that was present at time T1, eg, before degradation occurs. Returned.

  At time T3, the finger activation circuit 125 may determine that the multi-finger device 105 is further degraded, eg, a second minimum amount of degradation. In response to determining that multi-finger device 105 has a second minimum amount of degradation, finger activation circuit 125 directs switch 115 to close through control signal 145. When switch 115 is closed at time T3, gate region 140C is coupled to the gate circuit node, and finger 3 is activated. For example, at time T3, the switch 115 further disconnects the gate region 140C from the ground. When fingers 1-3 are activated, the degradation that occurred in multi-finger device 105 after time T2, for example, the second minimum amount of degradation, can be overcome. Again, the degradation index of multi-finger device 105 can be returned to or near the reference level for that index that was present at time T1.

  At time T4, the finger activation circuit 125 may determine whether the multi-finger device 105 is still further degraded, eg, a third minimum amount of degradation. In response to determining that multi-finger device 105 has a third minimum amount of degradation, finger activation circuit 125 may instruct switch 120 to close through control signal 145. When switch 120 is closed at time T4, gate region 140D is coupled to the gate circuit node and finger 4 is activated. For example, at time T4, the switch 120 further disconnects the gate region 140D from the ground. When fingers 1-4 become active, the degradation that occurred in multi-finger device 105 after time T3, eg, a third minimum amount of degradation, can be overcome.

  In one embodiment, the minimum amount of first, second and third degradation is equal. In other embodiments, one or more or all of the minimum amounts of first, second and third degradations can be different amounts. For example, the minimum amount of first, second, and third degradation may be linear or non-linear with respect to each other when plotted or graphed. Finger activation circuit 125 may be configured to detect the same or different amounts of degradation at various time points during the life of multi-finger device 105.

  FIG. 2 is a second block diagram illustrating the system of FIG. 1 according to another embodiment disclosed herein. FIG. 2 shows an embodiment used to determine when the non-active fingers of a multi-finger device are to be activated as time is measured. For clarity and ease of illustration, the source circuit node, the drain circuit node, and the wiring that couples the multi-finger device 105 to the source circuit node and the drain circuit node are not shown. Thus, FIG. 2 shows multi-finger device 105, switches 110-120, and finger activation circuit 125. The finger activation circuit 125 includes a control circuit 205 and a counter 210. Where necessary or possible, similar numbers are used throughout the specification for the same items.

  FIG. 2 illustrates an embodiment that is used to determine when to activate device fingers when degradation data for the device is pre-collected and the device is operating and running. For example, one or more operating parameters of the device can be selected as a degradation indicator and observed over the lifetime of the device. A technique in which a selected degradation index, such as a device operating parameter, degrades or changes from a reference level over time can be used as a degradation measurement. A degradation measurement refers to a specific degradation index, eg, an operating parameter, or a plurality of such degradation indices. In one embodiment, the degradation measurement may identify an amount by which one or more degradation indicators have changed relative to a reference level for each of the degradation indicators used in determining the degradation measurement.

An example of a device operating parameter that can be used as a degradation indicator that can be observed over time may include a drain saturation current commonly _denoted as I _dsat . Device degradation can be observed in the form of a decrease in I _dsat compared to a reference level of I _dsat over the lifetime of the device, as measured in changes in the device's I _dsat . Other examples of device operating parameters that can be used as degradation indicators that can be observed over time may include a threshold voltage commonly denoted as V _t . Deterioration of the device, as measured in a change in device V _t, is observable reduction in the form of V _t compared to the reference level V _t across the life of the device.

  Thus, one or more operating parameters are compared to a selected reference level for each operating parameter used to determine the amount that the operating parameter or collection of operating parameters changes over time, thereby allowing the device to Used as a degradation measurement or used to formulate. The reference level can be a specification requirement, the beginning of a device lifetime, for example, an initial value of an operating parameter before degradation, and the like.

  From the collected degradation data, the amount of device degradation time may be determined as a selected amount. For example, an amount of time for a selected operating parameter that deviates from a predetermined amount, or a percentage from a reference level for that operating parameter is determined. Additional periods in which the device degrades from the reference level by the same amount or the same percentage can also be identified. For example, the time when the device degrades by 10%, 20%, 30%, etc. from the reference level can be identified. Referring back to FIG. 2, the counter 210 is used to determine when the period of interest has elapsed, thereby allowing the multi-finger device 105 to be a specific amount related to the amount of time determined to have elapsed. Is expected to be degraded.

As shown, counter 210 may receive a reference clock signal 215 having a known frequency. Counter 210 may be configured to count clock edges, clock cycles, and the like. Further, the counter 210 may store one or more predetermined counts as degradation thresholds. Each degradation threshold may represent the amount of time required for multi-finger device 105 to degrade by a predetermined amount for one or more given degradation indicators. For purposes of illustration, consider each count corresponding to the amount of time required for the multi-finger device 105 to degrade 10% from a reference level. For example, if I _dsat is used as the degradation index, each count represents the amount of time for I _dsat of multi-finger device 105 required to degrade by 10% from the reference level I _dsat. If V _t is used as the deterioration index, each count represents the amount of time for the V _t of the multi-finger device 105 required to degrade the reference level V _t by 10%.

  Thus, the counter 210 can count selected edges of the reference clock signal 215. The value of the counter 210 is called a count. The counter 210 determines when the count reaches or exceeds each deterioration threshold and outputs a signal to the control circuit 205. For example, the counter 210 may include one or more comparators configured to compare the counter with a degradation threshold or a threshold stored in the counter 210. Each time the counter 210 determines that the count has reached the degradation threshold, the counter 210 outputs a signal to the control circuit 205.

In response to each signal or notification received from counter 210, control circuit 205 may close one or more of switches 110-120, thereby activating one or more of fingers 2-4. Such additional finger activation counteracts degradation in operating parameters such as I _dsat and / or V _t , thereby at or near the reference level of each individual operating parameter prior to degradation. Returns operating parameters.

  In one embodiment, a single degradation threshold can be stored. In such cases, the counter may be reset each time the count reaches the degradation threshold. In other embodiments, a plurality of different degradation thresholds are stored. For example, first, second and third deterioration threshold values are stored, and the first, second and third deterioration threshold values are different. For example, finger 2 may be activated when a first degradation threshold is reached. The finger 3 can be activated when the second degradation threshold is reached. Finger 4 can be activated when the third degradation threshold is reached.

  When using time to determine when to activate the second finger of multi-finger device 105, the specific environment in which the IC that includes multi-finger device 105 operates, and the device-specific factors affect the degradation rate. It should be understood that it can be given. The environment can be characterized by one or more factors, also called stressors. In general, the amount of time that the multi-finger device 105 is active, eg, at least one finger is active, thereby being exposed to a particular environmental stressor, determines the life of the multi-finger device 105 and It can be measured to determine the degradation rate of one or more operating parameters of finger device 105. Multi-finger device 105 is considered active at least while finger 1 is active. Thus, the IC is operable in that the gate region 140A is coupled to the gate circuit node and power is applied to the IC and finger 1 to be active.

  Examples of stressors may include, but are not limited to, ambient temperature, time spent by the multi-finger device 105 in different operating conditions, operating and / or switching frequency, and the like. These stressor values characterize the environment and affect the degradation rate of the multi-finger device 105. For example, the multi-finger device 105 degrades faster when operating and operating in an environment having a higher ambient temperature than in an environment having a low ambient temperature. The amount of time that the multi-finger device 105 is maintained in a particular operating state, such as having a particular bias, can increase or decrease the degradation rate. The frequency at which multi-finger device 105 switches states in the circuit, such as the operating frequency, can increase or decrease the rate of degradation. Although part of the environment of the multi-finger device 105, the amount of time that the multi-finger device 105 is maintained in a particular state and / or the frequency at which the multi-finger device switches states is arranged by the multi-finger device 105 Depends on specific circuit and application.

  Device specific factors that can change the degradation rate of the device include, but are not limited to, the process technology used to manufacture the device, and thus the size of the device (eg, gate length), and the power supply voltage of the device and / or IC Can be included.

  Thus, in one embodiment, for a particular environment where an IC including multi-finger device 105 is known and can be approximated or modeled, various time periods, such as degradation thresholds, are determined therefrom. Degradation data may be obtained by exposing the multi-finger device 105 or a test device substantially similar or identical to the multi-finger device 105 to the same or substantially similar stressor characterizing its environment. In this way, the data used to more accurately determine the various degradation thresholds reflects and tracks the “real world” usage of the multi-finger device 105 when operating in that field.

  FIG. 3 is a third block diagram illustrating the system of FIG. 1 according to another embodiment disclosed herein. FIG. 3 illustrates an embodiment in which the actual degradation indicator of the multi-finger device 105 used to determine degradation measurements is measured while the multi-finger device 105 is used in the field. As described with reference to FIG. 2, for clarity and ease of illustration, source circuit nodes, drain circuit nodes, and wiring that couples multi-finger device 105 to source and drain circuit nodes are not shown. . FIG. 3 shows multi-finger device 105, switches 110-120, and finger activation circuit 125.

Finger activation circuit 125 includes a control circuit 205 and a measurement circuit 305. Any of a variety of different measurement circuits or systems can be used to obtain real time readings or samples of the degradation indicators discussed herein. An example of a measurement circuit that can be used is Keane et al. “An On-Chip NBTI Sensor for Measuring PMOS Threshold Voltage Degradation”, Very Large Scale Integration (VLSI) system under review at IEEE conference, 2008. However, other types of measurement circuits known in the field can be used to obtain real time measurements for I _dsat and / or V _t on the same IC or in the IC as the multi-finger device 105, so The examples given are not intended to be limiting.

FIG. 3 illustrates an embodiment that operates substantially as described herein, except that real-time measurements of operating parameters of the multi-finger device 105 are made and compared to a reference level. For example, the measurement circuit 305 may be configured to measure I _dsat , V _t , or both I _dsat and V _t . The measurement circuit 305 is configured to store one or more degradation thresholds, each degradation threshold specifying a level of one of the degradation indicators. Therefore, while the degradation threshold value defines time in FIG. 2, the degradation threshold value defines I _dsat , V _t , or both in FIG.

  Accordingly, the measurement circuit 305 may be configured to compare a real-time measurement value of one of the deterioration indicators with a stored deterioration threshold value corresponding to the measured deterioration threshold value. The measurement circuit 305 can further determine when the degradation index reaches the degradation threshold. For example, the measurement circuit 305 may include one or more comparators configured to compare the measured value of the degradation index with a corresponding degradation index.

  Each time the measurement circuit 305 determines that the degradation threshold has been crossed, for example, that the selected operating parameter has been found to have degraded by a minimum amount from the reference level, the measurement circuit 305 controls. A signal or command is given to the circuit 205. In response to that signal or notification from the measurement circuit 305, the control circuit 205 closes one or more of the switches 110-120, thereby activating one or more of the fingers 2-4. . As a result of activation of one or more of the fingers 2-4, degraded operating parameters can be pulled back to or near a reference level.

The embodiment shown in FIG. 3 can suppress degradation associated with I _dsat and V _t without requiring prior knowledge of the specific operating environment in which the multi-finger device 105 operates. In this regard, the embodiment of FIG. 3 can be considered more dynamic than the embodiment shown in FIG. This is because the real-time behavior specific measurement allows the finger activation circuit 125 to adapt to changing, unknown or unexpected environmental conditions.

  It should be understood that the number of fingers used in a multi-finger device configured as described with reference to FIGS. 1-3 is not limited to four. In some cases, multi-finger devices with fewer or more fingers may be used in combination with fewer or more switches. Further, although multi-finger device 105 is shown in FIGS. 1-3 as having fingers of substantially equivalent length, this need not be the case. For example, the size of secondary fingers, eg, initially inactive fingers, may be different from each other and the size of the primary fingers. The size of the primary finger can be determined based on design requirements for the multi-finger device with reference to the particular circuit in which the multi-finger device 105 is to operate. The size of the secondary finger of the device can be related to the amount of degradation to be suppressed over a selected period of time.

For example, each time a device degrades by 10% from a reference level, if one or more secondary fingers are activated to suppress 10% degradation, activate a specific number “N” of secondary fingers. However, the secondary fingers are sized so that a degradation index such as I _dsat or V _t is _pulled back to the reference level. Here, N is an integer of 1 or more. As will be appreciated, N may be selected to be 1, 2, 3, 4 or more fingers.

Furthermore, the multi-finger device may have one or more primary fingers, for example 2, 3 or more. Consider a multi-finger device with 10 primary fingers and each primary finger participating in 10 units of I _dsat so that the total I _dsat of the multi-finger device is approximately 100 units. In this example, 100 units of I _dsat corresponds to a reference level where no degradation has occurred. After two years of operation, the multi-finger device may degrade to provide only 70 units of I _dsat , corresponding to 30% degradation from the reference level. After five years of operation, the multi-finger device can be further degraded to provide only 50 units of I _dsat , corresponding to 50% degradation from the reference level. After 10 years of operation, the multi-finger device can be further degraded to provide only 30 units of I _dsat , corresponding to 70% degradation from the reference level.

By adding seven secondary fingers having substantially the same size as each of the primary fingers, the seven secondary fingers of the device can be activated over time to combat 10 years of degradation. For example, the degradation measurement I _dsat in this example activates the secondary finger and returns I _dsat to the reference level each time it determines a 10 unit decrease corresponding to the degradation threshold, Increase I _dsat by 10 units. This continues until each of the seven secondary fingers is activated, thereby countering 10 years of degradation in multi-finger devices.

  The system described with reference to FIGS. 1-3 may be configured to add one or more secondary fingers depending on a first amount of degradation from a reference level of the multi-finger device. The system may subsequently add one or more secondary fingers in response to a second amount of degradation from a multi-finger device degradation that is different from the first amount of degradation. The added secondary fingers can vary based on the amount of degradation to counter and the size of the secondary fingers.

  In other embodiments, the number of fingers activated in response to reaching each degradation threshold may vary. For example, in response to reaching a degradation threshold, such as the first degradation threshold, a first number of secondary fingers may be activated. In response to reaching another degradation threshold, eg, a second degradation threshold, a second number of secondary fingers different from the first number may be activated.

FIG. 4 is a first graph 400 illustrating the calibration of a multi-finger device according to another embodiment disclosed herein. More specifically, FIG. 4 shows how a device's I _dsat can degrade over time. The dotted line shows how I _dsat decreases over time when the device is exposed to a particular stressor as disclosed herein. If no calibration is applied, I _dsat continues to decline over time until the device eventually _fails .

At time T1, the primary finger of the multi-finger device is active. The secondary finger used for calibration is not active. At time T1, the level of I _dsat is a reference level. Over time, the level of I _{dsat in} the device decreases, indicating degradation. At time T2, the level of I _dsat reaches the deterioration threshold value by actual measurement or estimation based on elapsed time. Accordingly, at time T2, one or more secondary fingers are activated, thereby _returning the level of I _dsat in the multi-finger device to a reference level. After time T2, the multi-finger device continues to _degrade with I _dsat continually decreasing. At time T3, the degradation threshold is reached again, and additional secondary fingers are activated to increase I _dsat to the reference level.

In some cases, I _dsat can degrade in a substantially linear fashion. For example, I _dsat can degrade in a non-linear manner due to various factors such as the multi-finger device is not always active in the circuit or is not active in a stationary manner. In this regard, the x-axis (time), the y-axis (I _dsat ), or both can be non-linear. For example, the x-axis, y-axis, or both can be specified on a logarithmic scale.

FIG. 5 is a second graph 500 illustrating calibration of a multi-finger device according to another embodiment disclosed herein. More specifically, Figure 5 illustrates how V _t in the device is degraded how over time. The dotted line shows how V _t decreases with time when the device is exposed to a particular stressor as disclosed herein. If the calibration is not applied, the device until no finally function, V _t continues to decrease with time.

At time T1, the primary finger of the multi-finger device is active. The secondary finger used for calibration is not active. At time T1, the level of V _t is the reference level. Over time, the level of V _t in the device decreases, indicating a deterioration. At time T2, the estimation based on actual measurement or the elapsed time, the level of V _t reaches the deterioration threshold. In response, at time T2, one or more secondary fingers are activated, thereby returning the level of V _t in the multi-finger device to a reference level. After time T2, the multi-finger device continues to degrade with V _t continuing to decline. At time T3, again reaches the deterioration threshold, and additional secondary finger is activated to increase the V _t to the reference level.

As discussed with respect to FIG. 4, in some cases, V _t may degrade in a substantially linear fashion. In other cases as already described herein, V _t may be degraded by nonlinear manner. In this regard, the x-axis (time), the y-axis (V _t ), or both can be non-linear. For example, the x-axis, y-axis, or both can be specified on a logarithmic scale.

  FIG. 6 is a first flowchart illustrating a method 600 for collecting calibration data for a device in an IC according to another embodiment disclosed herein. Method 600 may be implemented using an IC test system coupled to a data processing system. IC test systems are well known in the art and can be communicatively linked to a data processing system that can collect, store, and manipulate data acquired from the IC during testing, such as a computer system.

  An example data processing system may include at least one processor coupled to a memory element via a system bus. The data processing system can store program code in a memory element, whereby a processor can execute program code that is accessed from the memory element via a system bus. A memory element may include one or more physical memory devices, such as, for example, local memory and one or more mass storage devices. Local memory refers to random access memory or other non-persistent memory devices that are commonly used during the actual execution of program code. Mass storage may be implemented as a hard drive or other persistent data storage. The data processing system may also include one or more cache memories that provide temporary storage of at least some program code to reduce the number of times program code is called from mass storage during execution. .

  Input / output (I / O) devices such as a keyboard, display, and pointing device may optionally be coupled to the data processing system. The I / O device may be coupled directly to the data processing system or may be coupled via an intermediate I / O controller. A network adapter is also coupled to the data processing system so that the system can be coupled to other systems, computer systems, remote printers, and / or remote storage devices through an intermediate personal network or public network. To do. Modems, cable modems, and Ethernet cards are examples of different types of network adapters that can be used with a data processing system.

  In step 605, a device in the IC, such as a multi-finger device, may be exposed to a selected environment having a known stressor. As described above, the environment includes the ambient temperature surrounding the IC or test system, the specific circuit design that is operating on the IC that the device is part of during testing, the time spent by the device in a specific state, and the operation Characterized by a stressor such as frequency and / or switching of devices during testing. In addition, IC and device characteristics, such as specific factors, such as device and element sizes or sizes of different regions of the device, specific process technology used to implement the device and / or IC, etc. are known. It is. Information such as described above may be stored and / or associated with acquired and / or collected degradation data.

In step 610, a degradation indicator may be measured over time. For example, an IC may include one or more measurement circuits that are coupled to the device during testing. The measurement circuit may measure I _dsat , V _t , or both I _dsat and V _t over time, while the device and IC under test are operating in that environment. The measurement circuit may be configured to output degradation indicator measurements to the data processing system via one or more pins of the IC.

  In other examples, external measurement equipment may be used to verify or otherwise couple with the IC, measure the degradation indicator over time, and provide the measurement to the data processing system. Time stamp information determined from the internal clock of the IC and output together with the measurement value of the deterioration index, or time stamp information provided by another source outside the IC provided to the data processing system is associated with the measurement value of the deterioration index. It should be understood that you get.

In step 615, the degraded data set may be stored. A degradation indicator may be provided to the data processing system for storage. For example, records are generated and stored in the data processing system, each record including V _t and / or I _dsat , along with a time stamp that identifies when the value was measured. The degraded data set may include a plurality of such records that span a selected time period. As described above, the degradation data set may be associated with the environment used for testing and device specific parameters.

  At step 620, a degradation threshold can be determined from the degradation data set. At step 625, a time stamp associated with each degradation threshold may be identified. At step 630, the data processing system knows the time stamp and the reference clock to be used to measure the time in the finger activation circuit based on the start time of the test, as described herein. To a count based on the frequency of

As discussed with reference to FIGS. 3 and 4, the amount of time that the device degrades can be a non-linear feature in either I _dsat or V _t perspective. Thus, a count that serves as an amount of time, or degradation threshold, may not be associated on a linear scale.

  In step 635, the count for each degradation threshold is stored in the data processing system and used in the finger activation circuit of the IC to be sent to the field.

  It should be understood that the method 600 can also be performed for multi-finger devices where a degradation indicator is observed when a secondary finger is activated over time to determine a more accurate degradation threshold. .

  FIG. 7 is a second flowchart illustrating a method 700 for calibrating a multi-finger device according to another embodiment disclosed herein. The method 700 may be performed by a system as described with reference to FIGS. 1-6 herein. Thus, the method 700 begins at step 705 where the multi-finger device begins operating in the IC. A multi-finger device may initiate operation with a predetermined number of active fingers, eg, primary fingers. A secondary finger is a finger of a multi-finger device that, as described above, is initially deactivated and can be used to overcome multi-finger device degradation over time.

In step 710, the finger activation circuit may determine and monitor one or more degradation indicators, eg, degradation measurements. In embodiments where time is used as a degradation indicator, the finger activation circuit may determine and monitor the count of a counter configured to count selected edges of the reference clock. In embodiments where real-time measurements of quantities such as V _t and / or I _dsat are used as degradation indicators, those quantity measurements obtained from the multi-finger device during operation can be determined and monitored. .

In step 715, the finger activation circuit may determine whether the degradation indicator or degradation measurement value satisfies a degradation threshold. For example, meeting the degradation threshold may include a count that is equal to or exceeds the threshold count identified as the degradation threshold. _Satisfying the degradation threshold may include degradation indicators such as I _{dsat that} are equal to or greater than some predetermined amount of I _dsat level that is greater than the reference level of I _dsat . Satisfy the degradation threshold may further include a deterioration index as a level equal to or less than V _t of V _t small number of predetermined amount than the reference level V _t.

  In response to determining that the degradation index satisfies the degradation threshold in the finger activation circuit, method 700 proceeds to step 720. In response to determining that the degradation indicator does not meet the degradation threshold in the finger activation circuit, the method 700 loops back to step 710 to determine and monitor one or more of the degradation indicators. continue.

  Continuing with step 720, the finger activation circuit may activate the “N” secondary fingers of the multi-finger device. As described above, N represents an integer value of 1 or more depending on the manner in which the secondary fingers of the multi-finger device are designed and the amount of degradation to be overcome. Further, the secondary fingers that are activated are those that were initially deactivated when the multi-finger device began operating in the IC.

  One or more embodiments disclosed herein allow a multi-finger device to be continuously calibrated over a selected span of time. Additional fingers that were initially deactivated are selectively activated over time to compensate for degradation that occurs over the life of the multi-finger device. Calibration allows the multi-finger device to be designed to closely match certain tolerances as opposed to those that are not suitable for overdesign and the intended purpose of the multi-finger device.

  The flowcharts in the figures illustrate the architecture, functionality, and operation of possible implementations of systems, methods and computer program products according to one or more embodiments disclosed herein. In this regard, each block in the flowchart represents a module, segment, or portion of code that includes one or more portions of executable program code that implement a particular logic function.

  It should be noted that in some alternative embodiments, the functions described in the blocks may occur out of the order described in the figures. For example, two blocks shown in succession may actually be executed substantially simultaneously, depending on the function involved, or the blocks may sometimes be executed in reverse order. . Each block in the flowchart illustration, and combinations of blocks in the flowchart illustration, may be implemented by a special purpose hardware-based system that performs a specific function or action, or special purpose hardware and executable instructions; It may be realized by a combination of

  One or more embodiments may be implemented in hardware or a combination of hardware and software. One or more embodiments may be implemented in a centralized manner within one system, or may be implemented in a distributed manner in which different elements are spread over several interconnected systems. Good. Any type of data processing system or other apparatus adapted to perform at least a portion of the methods disclosed herein is suitable.

  One or more embodiments may be embedded within a device, such as a computer program product, which includes all features that enable execution of the methods disclosed herein. The device includes a data storage medium that stores program code, such as a persistent computer-usable medium or computer-readable medium, which is loaded and executed in a system having a memory and a processor. And causing the system to perform at least some of the functions disclosed herein. Examples of data storage devices may include, but are not limited to, optical media, magnetic media, magneto-optical media, computer memory such as random access memory, mass storage devices such as hard disks, and the like.

  The terms “computer program”, “software”, “application”, “computer-usable program code”, “program code”, “executable code”, and variations and / or combinations thereof, are used herein. A specific function can be directly applied to a system having information processing capability, or after one or both of the following: a) conversion to another language, code, or notation, and b) reproduction in different material forms Means any representation in any language, code, or notation of a set of instructions intended to be executed. For example, program code includes, but is not limited to, subroutines, functions, procedures, object methods, object execution, executable applications, applets, servlets, source code, object code, shared / dynamic loading libraries, and / or computers. It may include other series of commands designed for execution on the system.

  As used herein, the terms “a” and “an” are defined as one or more. As used herein, the term “plurality” is defined as two or more. As used herein, the term “another” is defined as at least a second or more. The terms “including” and / or “having” as used herein are defined as comprising, ie, open language. As used herein, the term “coupled” means directly connected without other intermediate elements, or indirectly with one or more intermediate elements, unless otherwise indicated. Is defined as The two elements may be mechanically, electrically coupled or may be communicatively linked via a communication channel, path, network or system.

One or more embodiments disclosed herein may be incorporated in other forms without departing from the spirit or essential characteristics thereof. Accordingly, reference should be made to the following claims, rather than the foregoing specification, as indicating the scope of the one or more embodiments.

Claims (15)

A multi-finger device for realization in an integrated circuit,
A first finger configured to remain active;
A second finger that is initially deactivated at the same time as the first finger is active;
A finger activation circuit configured to selectively activate the second finger of the multi-finger device in response to determining that a degradation measurement for the multi-finger device satisfies a degradation threshold Including multi-finger devices. A switch coupled to the second finger;
The multi-finger device of claim 1, wherein the switch selectively couples the gate of the second finger to a data signal that is also coupled to the gate of the first finger.   The multi-finger device of claim 2, wherein the finger activation circuit includes a control circuit configured to provide a control signal to the switch in response to detecting the degradation threshold.   The finger activation circuit further comprises a monitor circuit configured to detect the degradation threshold by determining an amount of time that the first finger of the multi-finger device is active. The multi-finger device according to any one of 1 to 3.   The monitor circuit compares a count of the number of clock cycles in which the first finger of the multi-finger device is active to the degradation threshold and is responsive to the count being greater than or equal to the degradation threshold. The multi-finger device of claim 4, wherein the multi-finger device is configured to instruct the control circuit to activate the second finger.   The finger activation circuit detects the degradation threshold by measuring an operational parameter of the multi-finger device in the field, compares the operational parameter with the degradation threshold, and the operational parameter is the degradation The multi-finger of claim 3, further comprising a monitor circuit configured to instruct the control circuit to activate the second finger in response to determining that a threshold is met. device. The operating parameter is a threshold voltage of the multi-finger device;
The multi-finger device according to claim 6, wherein the deterioration threshold value defines a threshold voltage level that is greater than a reference level of the threshold voltage. The operating parameter is a drain saturation current of the multi-finger device;
The multi-finger device according to claim 6, wherein the deterioration threshold value defines a drain saturation current level smaller than a reference level of the drain saturation current.   9. The multi-finger device according to claim 1, wherein the gate of the second finger is coupled to the power supply potential of the integrated circuit when not active. A method for calibrating the performance of a multi-finger device in an integrated circuit (IC) comprising:
Determining degradation measurements for the multi-finger device in the IC;
Comparing the degradation measurement with a degradation threshold;
Activating a finger of the multi-finger device in response to determining that the degradation measurement satisfies the degradation threshold. Selecting the degradation measurement to include an amount of time that the multi-finger device is active;
The method of claim 10, further comprising selecting the degradation threshold to be a predetermined amount of time. Determining the amount of time that the multi-finger device is active according to the number of clock cycles counted in a counter implemented in the integrated circuit;
The method of claim 11, wherein the clock cycle number is compared to a clock cycle number threshold that represents the predetermined amount of time of the degradation threshold. Selecting the degradation measurement to include a threshold voltage of the multi-finger device;
11. The method of claim 10, further comprising selecting the degradation measurement to be a threshold voltage level of the multi-finger device that is greater than a reference level of the threshold voltage. Selecting the degradation measurement to include the drain saturation current of the multi-finger device;
11. The method of claim 10, further comprising selecting the degradation measurement to include a drain saturation current level of the multi-finger device that is less than a reference level of the drain saturation current.   15. The method of any one of claims 10-14, wherein the multi-finger device comprises a primary finger that is active prior to activation of any additional fingers of the multi-finger device.